The present invention relates to a bypass diode for a photovoltaic cell, of particular but by no means exclusive application in photovoltaic cell modules for use in solar concentrators of solar photovoltaic power systems.
Multijunction solar cells are used in solar concentrator photovoltaic power systems for generating power owing to their high efficiency. Although such solar cells are expensive, these efficiencies are sufficiently high to render such arrangements economically feasible. However, to maintain the reliability of such arrangements in which multiple cells are arranged in series, it is desirable to have a bypass diode for each cell in a series. The bypass diode prevents overloading of its corresponding cell when that cell has a reduced power output owing to poor illumination or performance, or some other malfunction. This allows the rest of the series of cells constituting a module to continue operating.
The number of cells in series, which determines the bus voltage, is usually greater than a hundred, so the bypassing of a single, failed cell will result in a power loss of 1% or less. The bypass diodes thus allow the system to keep operating with minimal loss of output.
One existing system is illustrated in U.S. Pat. No. 6,020,555, in which each cell is connected in parallel with its corresponding bypass diode resulting in a series of diodes in parallel with a series of cells.
However, in existing arrangements, where the bypass diodes are essentially adjacent to the cells, are unsuitable for systems with closely packed cells, such as dish concentrator or central receiver systems.